Dynamic range is the ratio of intensity of the highest luminance parts of a scene and the lowest luminance parts of a scene. For example, the image projected by a video projection system may have a maximum dynamic range of 300:1.
The human visual system is capable of recognizing features in scenes which have very high dynamic ranges. For example, a person can look into the shadows of an unlit garage on a brightly sunlit day and see details of objects in the shadows even though the luminance in adjacent sunlit areas may be thousands of times greater than the luminance in the shadow parts of the scene. To create a realistic rendering of such a scene can require a display having a dynamic range in excess of 1000:1. The term “high dynamic range” means dynamic ranges of 800:1 or more.
Modern digital imaging systems are capable of capturing and recording digital representations of scenes in which the dynamic range of the scene is preserved. Computer imaging systems are capable of synthesizing images having high dynamic ranges. However, current display technology is not capable of rendering images in a manner which faithfully reproduces high dynamic ranges.
Blackham et al., U.S. Pat. No. 5,978,142 discloses a system for projecting an image onto a screen. The system has first and second light modulators which both modulate light from a light source. Each of the light modulators modulates light from the source at the pixel level. Light modulated by both of the light modulators is projected onto the screen.
Gibbon et al., PCT application No. PCT/US01/21367 discloses a projection system which includes a pre modulator. The pre modulator controls the amount of light incident on a deformable mirror display device. A separate pre-modulator may be used to darken a selected area (e.g. a quadrant).
There exists a need for cost effective displays capable of reproducing a wide range of light intensities in displayed images.